Bucket assembly for turbine system

ABSTRACT

A bucket assembly for a turbine system is disclosed. The bucket assembly includes a main body having an exterior surface and defining a main cooling circuit, and a platform surrounding the main body and at least partially defining a platform cooling circuit. The platform includes a forward portion and an aft portion each extending between a pressure side slash face and a suction side slash face and further includes a forward face, an aft face, and a top face. The platform cooling circuit includes an upper surface and a lower surface. The bucket assembly further includes a passage extending between and providing fluid communication between the main cooling circuit and the platform cooling circuit. An end opening of the passage is defined in the lower surface of the platform cooling circuit.

FIELD OF THE INVENTION

The subject matter disclosed herein relates generally to turbinesystems, and more specifically to bucket assemblies for turbine systems.

BACKGROUND OF THE INVENTION

Turbine systems are widely utilized in fields such as power generation.For example, a conventional gas turbine system includes a compressor, acombustor, and a turbine. During operation of the gas turbine system,various components in the system are subjected to high temperatureflows, which can cause the components to fail. Since higher temperatureflows generally result in increased performance, efficiency, and poweroutput of the gas turbine system, the components that are subjected tohigh temperature flows must be cooled to allow the gas turbine system tooperate at increased temperatures.

Various strategies are known in the art for cooling various gas turbinesystem components. For example, a cooling medium may be routed from thecompressor and provided to various components. In the compressor andturbine sections of the system, the cooling medium may be utilized tocool various compressor and turbine components.

Buckets are one example of a hot gas path component that must be cooled.For example, various parts of the bucket, such as the airfoil, theplatform, the shank, and the dovetail, are disposed in a hot gas pathand exposed to relatively high temperatures, and thus require cooling.Various cooling passages and cooling circuits may be defined in thevarious parts of the bucket, and cooling medium may be flowed throughthe various cooling passages and cooling circuits to cool the bucket.

One specific component of a bucket that requires cooling is theplatform. Thus, a platform cooling circuit is provided in many knowbuckets. A typical platform cooling circuit includes an inlet portionthat extends from the platform to the shank of the bucket in acurvilinear fashion. Specifically, a curvilinear portion of the inletportion is typically located near an exterior intersection between theplatform and shank. Thus, during operation of the bucket, when theplatform and shank are subjected to differing temperatures, thistemperature differential may create significant bending stresses at thecurvilinear portion of the inlet portion. These stresses can lead to alow thermal fatigue life, and thus require frequent repair orreplacement of buckets.

Accordingly, an improved bucket assembly for a turbine system is desiredin the art. Specifically, a bucket assembly with an improved platformcooling circuit would be advantageous.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one embodiment, a bucket assembly for a turbine system is disclosed.The bucket assembly includes a main body having an exterior surface anddefining a main cooling circuit, and a platform surrounding the mainbody and at least partially defining a platform cooling circuit. Theplatform includes a forward portion and an aft portion each extendingbetween a pressure side slash face and a suction side slash face andfurther includes a forward face, an aft face, and a top face. Theplatform cooling circuit includes an upper surface and a lower surface.The bucket assembly further includes a passage extending between andproviding fluid communication between the main cooling circuit and theplatform cooling circuit. An end opening of the passage is defined inthe lower surface of the platform cooling circuit.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a schematic illustration of a gas turbine system according toone embodiment of the present disclosure;

FIG. 2 is a perspective view of a bucket assembly according to oneembodiment of the present disclosure;

FIG. 3 is a front view illustrating the internal components of a bucketassembly according to one embodiment of the present disclosure;

FIG. 4 is a partial perspective view illustrating the internalcomponents of a bucket assembly according to one embodiment of thepresent disclosure; and

FIG. 5 is a perspective view of a platform cooling circuit and passageaccording to one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

FIG. 1 is a schematic diagram of a gas turbine system 10. The system 10may include a compressor 12, a combustor 14, and a turbine 16. Thecompressor 12 and turbine 16 may be coupled by a shaft 18. The shaft 18may be a single shaft or a plurality of shaft segments coupled togetherto form shaft 18.

The turbine 16 may include a plurality of turbine stages. For example,in one embodiment, the turbine 16 may have three stages. A first stageof the turbine 16 may include a plurality of circumferentially spacednozzles and buckets. The nozzles may be disposed and fixedcircumferentially about the shaft 18. The buckets may be disposedcircumferentially about the shaft and coupled to the shaft 18. A secondstage of the turbine 16 may include a plurality of circumferentiallyspaced nozzles and buckets. The nozzles may be disposed and fixedcircumferentially about the shaft 18. The buckets may be disposedcircumferentially about the shaft 18 and coupled to the shaft 18. Athird stage of the turbine 16 may include a plurality ofcircumferentially spaced nozzles and buckets. The nozzles may bedisposed and fixed circumferentially about the shaft 18. The buckets maybe disposed circumferentially about the shaft 18 and coupled to theshaft 18. The various stages of the turbine 16 may be at least partiallydisposed in the turbine 16 in, and may at least partially define, a hotgas path (not shown). It should be understood that the turbine 16 is notlimited to three stages, but rather that any number of stages are withinthe scope and spirit of the present disclosure.

Similarly, the compressor 12 may include a plurality of compressorstages (not shown). Each of the compressor 12 stages may include aplurality of circumferentially spaced nozzles and buckets.

One or more of the buckets in the turbine 16 and/or the compressor 12may comprise a bucket assembly 30, as shown in FIGS. 2 through 5. Thebucket assembly 30 may include a main body 32 and a platform 34. Themain body 32 typically includes an airfoil 36 and a shank 38. Theairfoil 36 may be positioned radially outward from the shank 38. Theshank 38 may include a root 40, which may attach to a rotor wheel (notshown) in the turbine system 10 to facilitate rotation of the bucketassembly 30.

In general, the main body 32 has an exterior surface. In embodimentswherein the main body 32 includes an airfoil 36 and shank 38, forexample, the portion of the exterior surface defining the airfoil 36 mayhave a generally aerodynamic contour. For example, the airfoil 32 mayhave an exterior surface defining a pressure side 42 and suction side 44each extending between a leading edge 46 and a trailing edge 48.Further, the portion of the exterior surface of the shank 38 may includea pressure side face 52, a suction side face 54, a leading edge face 56,and a trailing edge face 58.

The platform 34 may generally surround the main body 32, as shown. Atypical platform may be positioned at an intersection or transitionbetween the airfoil 36 and shank 38 of the main body 32, and extendoutwardly in the generally axial and tangential directions. It should beunderstood, however, that a platform according to the present disclosuremay have any suitable position relative to the main body 32 of thebucket assembly 30.

A platform 34 according to the present disclosure may include a forwardportion 62 and an aft portion 64. The forward portion 62 is that portionof the platform 34 positioned proximate the leading edge 46 of theairfoil 36 and the leading edge face 56 of the shank 38, while the aftportion 64 is that portion of the platform 34 positioned proximate thetrailing edge 48 of the airfoil 36 and the trailing edge 58 of the shank36. The forward portion 62 and the aft portion 64 may further define atop face 66 of the platform 34, which may generally surround the airfoil36 as shown. Further, a peripheral edge may surround the forward portion62, aft portion 64, and top face 66. The peripheral edge may include apressure side slash face 72 and suction side slash face 74, which eachof the forward portion 62 and the aft portion 64 may extend between. Theperipheral edge may further include a forward face 76, which may definea peripheral edge of the forward portion 62, and an aft face 78, whichmay define a peripheral edge of the aft portion 64.

As shown in FIGS. 3 through 4, the main body 32 may define one or moremain cooling circuits therein. The main cooling circuits may extendthrough portions of the main body 32 to cool the main body 32. Forexample, in some embodiments as shown, the main body 32 may define aforward main cooling circuit 82 and an aft main cooling circuit 84. Themain cooling circuits may have any suitable shape and may extend alongany suitable path. For example, as shown each main cooling circuit mayhave various branches and serpentine portions and may extend through thevarious portions of the main body 32, such as through the airfoil 36 andshank 38. A cooling medium may be flowed into and through the variousmain cooling circuits 82 to cool the main body 32.

As further shown in FIGS. 3 through 5, one or more platform coolingcircuits 90 may be defined in the bucket assembly 30. In general, theplatform cooling circuit 90 may be defined at least partially in theplatform 34. For example, in exemplary embodiments, a portion of theplatform cooling circuit 90 is defined in the platform 34, and extendsthrough the platform 34 to cool it. Other portions of the platformcooling circuit 90 may extend into the main body 32 to inlet coolingmedium into the platform cooling circuit 90 (not shown) or exhaust thecooling medium therefrom. In one embodiment, as shown in FIG. 3, aplatform cooling circuit 90 may include a forward portion 92 asdiscussed below, an intermediate portion 94, and/or an outlet portion96. The outlet portion 96 may extend from the platform 34 into the mainbody 32, and the forward portion 92 and intermediate portion 94 mayextend through the platform 34. Cooling medium may flow through theforward portion 92 and intermediate portion 94, and be exhausted throughthe outlet portion 96.

In many bucket assemblies 30, a platform cooling circuit 90 is in fluidcommunication with a main cooling circuit, such that cooling medium isflowed from a main cooling circuit into the platform cooling circuit 90and/or is flowed from a platform cooling circuit 90 to a main coolingcircuit. For example, in the embodiment shown in FIGS. 3 through 5, theoutlet portion 96 is in fluid communication with the aft main coolingcircuit 84.

A platform cooling circuit 90, or any portion thereof, may have anysuitable path through the platform 34. For example, the platform coolingcircuit 90 or any portion thereof may be generally linear or generallycurvilinear. In some exemplary embodiments, the platform cooling circuit90, such as the intermediate portion 94 thereof, may have a generallyserpentine path, as shown. Such serpentine path may include alternatinggenerally linear and generally curvilinear portions, such that coolingmedium may flow back and forth through such portions as it flows throughthe platform cooling circuit 90. It should be understood, however, thata platform cooling circuit 90 according to the present disclosure mayhave any suitable path through the platform 34.

A platform cooling circuit 90 according to the present disclosure mayfurther include an upper surface 102 and a lower surface 104. In someembodiments, such as wherein the platform cooling circuit 90, or anyportion thereof, has a oval or circular cross-section, the upper surface102 and lower surface 104 may be generally curvilinear, and may meet tofully define the platform cooling circuit 90. In other embodiments, aplatform cooling circuit 90 may further include one or more sidewalls(not shown). Each sidewall may extend between an upper surface 102 and alower surface 104. Upper surfaces 102 and lower surfaces 104 accordingto the present disclosure may have any suitable shape and size. Forexample, an upper surface 102 and/or lower surface may be planer, may becurvilinear as discussed, or may include suitable bends or otherdisruptions. An upper surface 102 and lower surface 104, along withoptional sidewalls, may define any suitable cross-sectional profile fora platform cooling circuit, such as rectangular, oval, triangular, orany other suitable polygonal shape.

A bucket assembly 30 according to the present disclosure may furtheradvantageously include one or more passages 110, as shown in FIGS. 3through 5. Each passage 100 extends between a main cooling circuit and aplatform cooling circuit 90. In exemplary embodiments, for example, apassage 110 may extend between a forward main cooling circuit 62 and aplatform cooling circuit 90. Alternatively, however, a passage 110 mayextend between an aft main cooling circuit 64 and a platform coolingcircuit 90. Each passage 110 may provide fluid communication betweensuch main cooling circuit and such platform cooling circuit 90. Thus, inexemplary embodiments, cooling medium may flow from the main coolingcircuit into the passage 110, and from the passage 110 to the platformcooling circuit 90. Alternatively, however, cooling medium may flow fromthe platform cooling circuit 90 into the passage 110, and from thepassage 110 into the main cooling circuit.

As shown, a passage 110 according to the present disclosure furtherincludes end openings 112. The end openings 112 act as the inlet andoutlet for the passage 110 for flow to and from the main cooling circuitand platform cooling circuit 90. Advantageously, an end opening 112 ofthe passage 110, such as the end opening 112 for flowing cooling mediumbetween the passage 110 and platform cooling circuit 90, is defined inthe lower surface 104 of the platform cooling circuit 90. In exemplaryembodiments as shown, such end opening 112 is an outlet, such thatcooling medium flows through the end opening 112 into the platformcooling circuit 90 from the passage 110. Such design of the passage 110and platform cooling circuit 90 may advantageously reduce stresses atthe intersection between the platform cooling circuit 90 and passage110. For example, by designing the passage 110 and platform coolingcircuit 90 such that an end opening 112 of the passage 110 is defined inthe lower surface 104 of the platform cooling circuit 90, theintersection between the passage 110 and platform cooling circuit 90 maybe spaced from the exterior intersection between the platform 34 andshank 38. Thus, during operation of the turbine system 10 when theplatform 34 and shank 38 are subjected to different temperatures,resulting bending stresses at the intersection of the passage 110 andplatform cooling circuit 90 may be reduced or eliminated.

In some embodiments, as shown, at least a portion of a passage 110 mayextend in a generally radial direction. The radial direction is thedirection between the root 40 and airfoil 36 of the bucket assembly, andmay be shown as a vertical direction in FIG. 3. Thus, as shown, at leasta portion of a passage 110 may extend in the generally radial direction.As shown, in exemplary embodiments, such portion may be the portion thatdefines an end opening 112, such as the end opening 112 that is definedin the lower surface 104 of the platform cooling circuit 90. Inembodiments wherein such portion extends in the radial direction,cooling medium flowing from the passage 110 into the platform coolingcircuit 90 may further advantageously impingement cool the upper surface102 of the platform cooling circuit 90, thus providing improved coolingto the platform 34.

As discussed above and shown in FIGS. 3 through 5, in some embodimentsthe platform cooling circuit 90 may include a forward portion 92 and anintermediate portion 94. Further, the end opening 112 of the passage 110that is defined in the lower surface 104 of the platform cooling circuit90 may be defined in the intermediate portion 94. The forward portion 92may thus be that portion of the platform cooling circuit 90 that isgenerally upstream of such end opening 112, such that the general flowpath of cooling medium from the passage 110 into and through theplatform cooling circuit 90 is away from the forward portion 92.

The arrows shown in FIG. 5 illustrate one embodiment of a general flowpath of cooling medium from the passage 110 into and through theplatform cooling circuit 90. As shown, a portion of the cooling mediummay, upon entering the platform cooling circuit 90, flow upstream intothe forward portion 92. This cooling medium may then continuedownstream, along the general flow path of the cooling medium throughthe intermediate portion 94 of the platform cooling circuit 90. In someembodiments as discussed above, the cooling medium 90 may further flowthrough an outlet portion 96 and be exhausted from the platform coolingcircuit 90.

In some embodiments as shown, a bucket assembly 30 according to thepresent disclosure may further include one or more exhaust passages 120.Each exhaust passage 120 may be defined in the platform 34, such as inthe aft portion 64 of the platform 34 and/or in the forward portion 62of the platform 34, and may be in fluid communication with the platformcooling circuit 90. For example, an exhaust passage 120 may be in fluidcommunication with a forward portion 92, intermediate portion 94, outletportion 96, and/or any other suitable portion of a platform coolingcircuit 90. Thus, cooling medium flowing through the platform coolingcircuit 90 may flow from the platform cooling circuit 90 into an exhaustpassage 120.

Each exhaust passage 120 may further include an outlet 122. The outlet122 may be defined in any suitable location on the platform 34, such ason the aft portion 64 and/or forward portion 62 of the platform 34. Forexample, an outlet 122 may be defined in the top face 66 as shown, or inthe suction side slash face 74, or in the pressure side slash face 72 asshown, or in the forward face 76, aft face 78, or any other suitablelocation on the platform 34, such as on the aft portion 64 and/orforward portion 62 of the platform 34. Cooling medium flowed through anexhaust passage 120 may thus be exhausted through the outlet 122 of thatexhaust passage 120. Additionally, in some embodiments, such exhaustedcooling medium may further advantageously act as a cooling film to coolthe exterior of the platform 34.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A bucket assembly for a turbine system,comprising: a main body having an exterior surface and defining a maincooling circuit; a platform surrounding the main body and at leastpartially defining a platform cooling circuit, the platform comprising aforward portion and an aft portion each extending between a pressureside slash face and a suction side slash face and further comprising aforward face, an aft face, and a top face, the platform cooling circuitcomprising an upper surface and a lower surface; and a passage extendingbetween and providing fluid communication between the main coolingcircuit and the platform cooling circuit, wherein an end opening of thepassage is defined in the lower surface of the platform cooling circuit.2. The bucket assembly of claim 1, wherein the main cooling circuit is aforward main cooling circuit.
 3. The bucket assembly of claim 1, whereinthe end opening is an outlet.
 4. The bucket assembly of claim 1, whereinat least a portion of the passage extends in a generally radialdirection.
 5. The bucket assembly of claim 4, wherein the portion of thepassage extending in the radial direction defines the end opening. 6.The bucket assembly of claim 1, wherein the platform cooling circuitcomprises a forward portion and an intermediate portion, and wherein theend opening of the passage is defined in the intermediate portion. 7.The bucket assembly of claim 1, wherein the platform cooling circuitfurther comprises an outlet portion.
 8. The bucket assembly of claim 1,wherein at least a portion of the platform cooling circuit has agenerally serpentine path.
 9. The bucket assembly of claim 1, furthercomprising an exhaust passage defined in the platform and in fluidcommunication with the passage.
 10. The bucket assembly of claim 9,wherein an outlet of the exhaust passage is defined in the top face ofthe platform.
 11. The bucket assembly of claim 9, wherein an outlet ofthe exhaust passage is defined in the pressure side slash face of theplatform.
 12. The bucket assembly of claim 1, wherein the main bodycomprises a shank and an airfoil.
 13. A turbine system, comprising: acompressor; a turbine coupled to the compressor; and a plurality ofbucket assemblies disposed in at least one of the compressor or theturbine, at least one of the bucket assemblies comprising: a main bodyhaving an exterior surface and defining a main cooling circuit; aplatform surrounding the main body and at least partially defining aplatform cooling circuit, the platform comprising a forward portion andan aft portion each extending between a pressure side slash face and asuction side slash face and further comprising a forward face, an aftface, and a top face, the platform cooling circuit comprising an uppersurface and a lower surface; and a passage extending between andproviding fluid communication between the main cooling circuit and theplatform cooling circuit, wherein an end opening of the passage isdefined in the lower surface of the platform cooling circuit.
 14. Theturbine system of claim 14, wherein the main cooling circuit is aforward main cooling circuit.
 15. The turbine system of claim 14,wherein the end opening is an outlet.
 16. The turbine system of claim14, wherein at least a portion of the passage extends in a generallyradial direction.
 17. The turbine system of claim 14, wherein theplatform cooling circuit comprises a forward portion and an intermediateportion, and wherein the end opening of the passage is defined in theintermediate portion.
 18. The turbine system of claim 14, wherein theplatform cooling circuit further comprises an outlet portion.
 19. Theturbine system of claim 14, wherein at least a portion of the platformcooling circuit has a generally serpentine path.
 20. The turbine systemof claim 14, further comprising an exhaust passage defined in theplatform and in fluid communication with the passage.